十万个为什么·科学启蒙30篇（3）

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为什么切洋葱会流泪

Cutting an onion damages its cells and releases enzymes that convert sulfur compounds into volatile gases.
One gas, syn-propanethial-S-oxide, rises into the air and dissolves in the moisture on your eyes’ surface.
This forms mild sulfuric acid, which irritates the cornea and triggers tear glands to flush it out.
Tears contain lysozyme—an enzyme that kills bacteria—so crying also protects your eyes from infection.
Chilling onions before cutting slows enzyme activity and reduces gas release significantly.
Using a sharp knife causes less cell damage than a dull one, lowering the amount of irritant produced.
Wearing swim goggles or cutting near a running fan helps divert the gas away from your face.
Onions bred for low sulfur content—like sweet Vidalias—produce far less of the tear-inducing compound.
Garlic and leeks cause similar reactions, but their gases are less airborne and more pungent-smelling.
Interestingly, some people lack the gene variant that makes them sensitive to this particular onion compound.

听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。

Chilling onions before cutting slows enzyme activity and reduces gas release significantly. 切之前冷藏洋葱可减缓酶活性，显著减少气体释放。
Tears contain lysozyme—an enzyme that kills bacteria—so crying also protects your eyes from infection. 泪水含有溶菌酶——一种杀菌酶，因此流泪还能保护眼睛免受感染。
Onions bred for low sulfur content—like sweet Vidalias—produce far less of the tear-inducing compound. 低硫品种洋葱（如甜味维达利亚洋葱）产生的催泪物质少得多。

这篇中文题目最接近哪一句？为什么切洋葱会流泪一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？切洋葱会破坏其细胞，释放酶类，将含硫化合物转化为挥发性气体。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） Why Do Onions Make You Cry? How to cook noodles A maths worksheet

Chilling onions before cutting slows enzyme activity and reduces gas release significantly.

Chilling onions before cutting slows enzyme activity and reduces gas release significantly.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：Chilling onions before cutting slows enzyme activity and reduces gas release significantly.